1. Field of the Invention
The present invention relates to a sprag type one-way clutch which is used in conjunction with an automatic transmission or the like for an industrial instrument such as an agricultural machinery, an automobile, a construction equipment, or the like.
2. Related Background Art
A conventional sprag type one-way clutch has, arranged between an outer race 100 and an inner race 200, as illustrated in FIGS. 31 and 32, a sprag 300 of a shape of, for example, a gourd, an annular retainer 700 made of a high rigidity material such as a steel plate or the like for retaining the sprag 300, and a ribbon spring 400 for urging the sprag 300 in an engagement (meshing) direction.
A plurality of the sprags 300 are respectively retained by windows of an outer cage 500 and an inner cage 600. On a one-way clutch 1000, an end bearing 800 is provided for concentrically maintaining at both axial ends thereof the outer race 100 and the inner race 200. One side of the end bearing 800 is retained by a snap ring 900 inserted into the outer race, and the other side by the retainer 700, so as not to be axially separable.
As it can be seen from FIG. 31, a part of the outer cage 500 protrudes toward an outer race to have an intercept (hatched portion) touching the outer race 100, causing a drag (drag torque) relative to the outer race.
FIGS. 33 and 34 illustrate details of the ribbon spring 400 used in the conventional one-way clutch described above. The ribbon spring 400 is an article manufactured from a thin steel plate by die-cutting or the like.
The ribbon spring 400 has side bars 440 extending on both longitudinal sides thereof substantially in parallel, and cross bars 410 longitudinally provided in a plurality for connecting side bars 440 on both sides. Window portions 430 each of which is surrounded by cross bars 410 and side bars 440 are longitudinally provided at equal intervals.
From a cross bar 410, a tab 450 extending toward the inside of a window portion 430 is provided. Of the ribbon spring 400, one longitudinal end of the ribbon spring 400 forms an end portion 460 (FIG. 34), and the other end forms a cross bar 410. The end portion 460 and the cross bar 410 of the other end portion are combined together to form an annular shape to be used in the one-way clutch 1000. On the side bar 440 and the tab 450, a wrinkle portion 420, convexly bent, is provided, and the wrinkle portion 420 absorbs stress and can mitigate, by a bend portion 470 provided in the vicinity of the end portion, mutual contact of the end portions of the ribbon spring when the ribbon spring is made circular and mounted on the cage.
FIG. 35 is a side view of a conventional ribbon spring 400 showing a wrinkle portion 420 and a bend portion 470.
A subassembly of a ribbon spring where sprags are incorporated is retained by two cages composing an inner cage and an outer cage.
The above-described conventional ribbon spring used for the one-way clutch has problems to be mentioned hereunder.
Firstly, the ribbon spring comprises a large number of parts. Secondly, reduction of mounting width has not been easy. Thirdly, as a wrinkle portion has to be convexly manufactured, workability has been difficulty. Fourthly, rigidity of the ribbon spring has been rather insufficient.